1. Field of the Invention
The present invention relates to a resin substrate, which has a substrate body and a pin serving as an input/output terminal, and more particularly to a resin substrate having a pin which can reliably be connected to a socket or another substrate.
2. Description of the Related Art
Conventionally, a structure has been known in which a pin serving as an input/output terminal is secured and stood erect on a substrate body made of an insulating material, such as resin, for example, epoxy resin, or composite material of the resin and glass fibers, the pin being secured and stood erect by using a Pb—Sn soldering material, such as Pb—Sn eutectic solder.
As the foregoing resin substrate, a resin substrate 101 structured, for example, as shown in FIG. 6 is exemplified. A substrate body 102 of the resin substrate 101 has a resin insulating layer 103 and a circuit layer (not shown). A first main surface 102A of the resin substrate 101 has a connection pad 104 formed thereon. A solder resist layer 105 is formed to reach the edge of the connection pad 104.
The pin 111 has a large-diameter portion 111A and a shaft portion 111b and having a structure that the overall surface is applied with Ni plating or Au plating (not shown). The large-diameter portion 111A of the pin 111 is secured with a soldering material 115 to be opposite to the connection pad 104 allowed to expose over the solder resist layer 105. The soldering material 115 for establishing the connection between the pin 111 and the substrate body 102 is welded to substantially the overall surface of the exposed connection pad 104 and portions of the large-diameter portion 111A and the shaft portion 111b such that the soldering material 115 forms substantially a truncated-cone fillet shape.
When the resin substrate 101 has been joined to the socket, a large gap DSA is formed between the first main surface 102A of the substrate body 102 and the upper surface SKA of the socket SK, for example, as shown in FIG. 7. When the resin substrate 101 is mounted on another substrate or the like, also a large gap is formed. The reason for this lies in that the soldering material 115 upwards moved and welded to the shaft portion 111b of the pin 111 when the pin 111 is soldered to the substrate body 102 substantially enlarges the diameter of the shaft portion 111b of the pin 111. Thus, the shaft portion 111B cannot sufficiently deeply be inserted into the socket SK or a through hole of the other substrate.
If the large gap is formed, the overall height realized after the resin substrate 101 has been joined to the socket SK or the like is enlarged excessively. Thus, a requirement for reducing the height cannot be met. The pin 111 of a type which projects over the first main surface 102A by a short length sometimes suffers from unsatisfactory reliability of the connection with the socket SK or the like. Moreover, a requirement for connecting the substrate made of the resin 101 and the socket SK or the other substrate to each other for a shortest distance cannot be met.
As the wettability between the soldering material 115 and the Au-plated layer on the surface of the pin 111 is improved, the height HSA of the soldering material 115 which upwards moves when the pin 111 is secured is enlarged. When the wettability is adjusted to reduce the height HSA of the soldering material 115 which upwards moves, it can be considered that the overall height realized after the resin substrate 101 has been joined to the socket SK or the like can be reduced.